This is a request for partial support of the Fifth International Workshop on Developmental Renal Physiology to be held in Tremezzo (Italy) on August 26-28, 1992. The field of developmental renal physiology emerged some 40 years ago, prompted by the finding that differences in renal function between infants and adults were not explained solely by differences in body size. It was, however, only in 1980 that those involved in the study of the maturing kidney had the opportunity to hold the First International Workshop on Developmental Renal Physiology. The success of the meeting encouraged us to organize three subsequent workshops, at three years intervals, in conjunction with the meetings of the International Pediatric Nephrology Association. The programs of these meetings reflect the progress made in this field of research. The Fifth International Workshop on Developmental Renal Physiology will be held at a time when renal physiologists, in an attempt to understand in greater depths various biologic processes, are becoming increasingly interested in their ontogeny. This tendency is reflected in the program which is heavily oriented towards cellular and molecular biology, and in the wide participation of scientists with backgrounds other than pediatrics. The meeting is scheduled for two and a half days. The first two half days will be dedicated to cellular growth and differentiation. The other sessions will be dedicated to topics of great current interest, namely vasoactive peptides, renal nerves, mineral transport, blood pressure control, concentrating mechanism, acid- base homeostasis, and to pathophysiological issues pertinent to the immature kidney. The sessions will be interspersed with provide not only an opportunity to review the progress made in the field of developmental renal physiology, but it will also serve as a forum for exchange of ideas and as a vehicle for introducing new methods of investigation applicable to the maturing kidney.